Debt - Short-Term Debt (Details) - USD ($) $ in Thousands			1 Months Ended			9 Months Ended
	Jan. 19, 2024	Dec. 05, 2023	May 31, 2023	Apr. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Jan. 20, 2023
Short-Term Debt [Line Items]
Short-term borrowings						$ 0	$ 306,400	$ 95,000
Repayment of short-term borrowings						$ 95,000	$ 193,500
Term Loan Agreement | Cascade Natural Gas
Short-Term Debt [Line Items]
Short-term borrowings									$ 150,000
Repayment of short-term borrowings	$ 50,000	$ 100,000
Term Loan Agreement | Intermountain Gas Company
Short-Term Debt [Line Items]
Short-term borrowings									$ 125,000
Repayment of short-term borrowings	$ 45,000		$ 30,000	$ 30,000	$ 20,000